Post on 17-Jul-2020
Validation of a Controlled Reception Pattern
Antenna (CRPA) Receiver Built from
Inexpensive General-purpose Elements During
Several Live Jamming Test Campaigns
Yu-Hsuan Chen, Stanford University
Sherman Lo, Stanford University
Dennis M. Akos, University of Colorado at Boulder
David S. De Lorenzo, Stanford University
Per Enge, Stanford University
BIOGRAPHY
Yu-Hsuan Chen is a Postdoctoral Scholar in the Stanford
GPS Laboratory. He received his Ph. D in electrical
engineering from National Cheng Kung University,
Taiwan in 2011. His research interests include real-time
GNSS software receiver and antenna array processing.
Sherman Lo is currently a senior research engineer at the
Stanford GPS Laboratory. He is the Associate
Investigator for the Stanford University efforts on the
FAA evaluation of alternative position navigation and
timing (APNT) systems for aviation. He received the
Ph.D. in Aeronautics and Astronautics from Stanford
University.
Dennis M. Akos obtained the Ph.D. degree from Ohio
University in 1997. He is an associate professor with the
Aerospace Engineering Science Department at University
of Colorado at Boulder with visiting appointments at
Luleå Technical University and Stanford University.
David S. De Lorenzo is a Principal Research Engineer at
Polaris Wireless and a consulting Research Associate to
the Stanford GPS Laboratory. His current research is in
adaptive signal processing, software-defined radios, and
navigation system security and integrity. He received the
Ph.D. degree in Aeronautics and Astronautics from
Stanford University and previously has worked for
Lockheed Martin and for the Intel Corporation.
Per Enge is a professor of Aeronautics and Astronautics
at Stanford University, where he is the Kleiner-Perkins
Professor in the School of Engineering. He directs the
Stanford GPS Laboratory, which develops satellite
navigation systems. He has been involved in the
development of the Federal Aviation Administration’s
GPS Wide Area Augmentation System (WAAS) and
Local Area Augmentation System (LAAS).
ABSTRACT
The Controlled Reception Pattern Antenna (CRPA) is an
effective approach for rejecting radio frequency
interference. Conventionally, the dedicated CRPA
antenna and hardware are usually precisely manufactured
and calibrated carefully. The computational/processing
requirement is always a major challenge for implementing
a CRPA receiver. Even more demanding would be to
incorporate the flexibility of the Software-Defined Radio
(SDR) design philosophy in such an implementation. The
Stanford University (SU) CRPA receiver development
tackles these challenges to try to demonstrate the
feasibility of a low cost commercial implementation by
leveraging a SDR using Commercial Off-the-Shelf
(COTS) components. This paper will discuss our real-
time implementation of a COTS CRPA software receiver,
its performance under numerous jamming conditions, and
the lessons learned from these various trials. The
developed CRPA receiver was tested in the live-jamming
exercises in the US and Sweden. The scenarios include 1)
dynamic jammers 2) static/multiple jammers in the
various locations 3) different jammer types.
This paper shows the test results including the C/No
improvement. From these results, we can see the benefit
of our implementation compared to a commercial
receiver. We also “replay” the signal from the collected
data sets. With this replay functionality, the signal from a
single antenna and the composite signals by
MVDR/power minimization algorithms are transmitted to
commercial high-sensitivity GPS receiver. The replay
results give us a true comparison between different
algorithms/platforms.
INTRODUCTION
Global Navigation Satellite System (GNSS) signals are
relatively weak and thus vulnerable to deliberate or
unintentional interference. An electronically-steered
antenna array system provides an effective approach to
mitigate interference by controlling the reception pattern
and steering beams/nulls. As a result, so-called Controlled
Reception Pattern Antenna (CRPA) arrays have been
deployed by organizations such as the US Department of
Defense which seeks high levels of interference rejection.
As GNSS is being increasing relied upon and integrated
into society, CRPA technology offers an important
capability to the civil community. CRPA technology
would provide robustness to critical infrastructure that
relies on GNSS for timing such as cellular
communication, and the power grid. This is important as
deliberate interference on GNSS is increasing. Its use
faces some major drawbacks such as cost and complexity.
Furthermore, CRPA was developed for military use and
the technology remains mostly in that domain. It has been
primarily a restricted technology.
Our efforts have focused on developing a commercially
viable CRPA system using Commercial Off-The-Shelf
(COTS) components to support the needs of Federal
Aviation Administration (FAA) alternative position
navigation and timing (APNT) efforts. In our previous
work on the CRPA receiver, two versions of the software
and a study on array geometry have been done. In 2010,
we implemented a 7-element, 2-bit-resolution, single-
beam and real-time CRPA software receiver under
Windows 7 [1]. The first version provided us experience
on implementing the CRPA algorithms in a software
receiver platform. However, it did not have enough
dynamic range in the front-end. In 2011, the receiver was
upgraded to support data collections with 14-bit-
resolution, and from 4 antenna elements. It was capable of
processing the data and steering twelve beams
simultaneous in real time. However, the implementation,
also under Windows 7, could only perform CRPA in post-
processing mode due to the interaction of the data
collection with Windows [2]. In 2012, we conducted a
study to investigate the antenna array geometry and
COTS antenna usage for the CRPA [3]. In this study, we
created a self-calibration procedure to use antenna arrays
built from COTS elements. And, we built a signal
collection hardware consisting of four Universal Software
Radio Peripheral 2 (USRP2) [4] and one host Personal
Computer (PC)
Leveraging on our prior work on the CRPA receiver, a
real-time CRPA software receiver under Ubuntu/Linux
was developed with following features: 1) high dynamic
range with 14-bit-resolution 2) all-in-view 12-channel
pre-correlation beamforming 3) built using inexpensive
COTS components including antenna and hardware 4)
beamforming and nulling using Minimum Variance
Distortionless Response (MVDR) and power
minimization (PM) algorithms 5) calibrating array
geometry and cable delay during runtime 6) temporal
processing for frequency nulling.
In order to validate the anti-jam (A/J) performance of the
Stanford University (SU) CRPA software receiver, the
receiver was taken to three live-jamming tests in 2012.
These tests generally included numerous different
jamming scenarios and included dynamic and static
jammers. The dynamic scenarios allowed for the
demonstration of the fast updating rate of beamforming
algorithm. Static single jammer power ramp scenarios
allowed for a controlled demonstration of the maximum
tolerable Jamming-to-Noise ratio (J/N) of the CRPA
receiver. These scenarios quantified the robustness the SU
CRPA receiver for different type of jammers. In scenarios
with multiple static jammers, the ability of the CRPA
receiver to mitigate several jammers from different
directions was assessed. Another test was to demonstrate
CRPA receiver capable of processing L5 signal and
mitigate L5 interference in the form of a high-power
Distance Measuring Equipment (DME) signal at 1173
MHz.
This paper is organized as follows. First, the hardware
and software architecture of our CRPA software receiver
are described. Then, an overview of field tests is given.
For each test, the representative scenarios are described in
detail and then test results are given between CRPA
processing and single antenna commercial receiver.
Finally, a summary of the work is presented.
HARDWARE ARCHITECTURE OF RECEIVER
The hardware architecture of CRPA software receiver is
depicted in figure 1. The CRPA hardware contains a 4-
element antenna array, four USRP2 software radio
systems [4] and one host computer with Solid-State Drive
(SSD) and is shown in figure 3. The signal received from
each antenna passes to a USRP2 board equipped with a
DBSRX2 programmable mixing and down-conversion
daughter board. The individual USRP2 boards are
synchronized by a 10 MHz external common clock
generator and a Pulse Per Second (PPS) signal. The
USRP2s are controlled by a host computer running the
Ubuntu distribution of Linux. The USRP Hardware
Driver (UHD) [5] software is used to configure USRP2
and daughter boards such as sampling rate and RF center
frequency. This flexible hardware set up supports a four
antenna signal collection system and real-time CRPA
software receiver for either L1 or L5 frequencies. The
radiofrequency (RF) signal from each antenna element is
converted to a near zero Intermediate Frequency (IF) and
digitized to 14-bit complex or in-phase and quadarature
outputs (I & Q, respectively). The RF center frequency
was set to 1575 MHz for L1 and 1176 MHz for L5. The
sampling rate was set to 4 MHz for L1 and 20 MHz for
L5. The host computer is equipped with 4-port Ethernet
card to receive the entire digital IF data with one port
dedicated to each USRP2. Then, the data is processed in
real-time and/or stored into SSDs in the host computer.
The flexible set up and SDR implementation allowed for
the use of different antenna elements and configurations.
The elements of antenna array can be arranged in layout
such as Y or square shapes. One tested COTS antenna
array is seen in figure 2. The electrical layout of antenna
array is calculated by a procedure described in [3].
USRP2Motherboard
DBSRX2Daughterboard
Host Computer
Ubuntu Linux
PPSSignal
External Clock
USRP2Motherboard
DBSRX2Daughterboard
USRP2Motherboard
DBSRX2Daughterboard
USRP2Motherboard
DBSRX2Daughterboard
Solid-State Drive
Figure 1. Block diagram of the CRPA software
receiver hardware
Figure 2. Photo of the COTS antenna array
Figure 3. Photo of the CRPA software receiver
hardware
SOFTWARE ARCHITECTURE OF RECEIVER
The software receiver [2][6][7][8][9] is developed in
Eclipse with the GNU C compiler. Most of source code is
programmed using C++. Assembly language is used to
program the functions with high computational
complexity such as correlation operations and weight-
and-sum. The software architecture of CRPA software
receiver is depicted in the figure 4. For each antenna
element, a set of 12 tracking channels are processed. Each
channel is dedicated to track the signal of single satellite.
All the channels are processed in parallel. The tracking
channels output carrier phase measurements to build the
steering vectors for each satellite. Two algorithms,
MVDR and power minimization, are adopted for
calculating the weights adaptively. There are 13 sets of
weights with 12 sets dedicated to each MVDR channel as
a set is needed for each desired beam direction or satellite.
One set used for power minimization which minimize
output power without regard to satellite directions. The
Space-Time Adaptive Processing (STAP) is also
implemented with the weight calculation performed for
each time tap. STAP provides enhanced anti-jamming
performance both in the frequency and spatial domains.
For the beamforming approach, the pre-correlation
beamformer is adopted to form 13 composite signals by
the multiplying weights with digital IF data and summed
over all elements shown in figure 5. Each composite
signal from MVDR is then processed by a single tracking
channel. Moreover, the composite signal from PM is then
processed by the other 12 tracking channels. Finally,
positioning is performed after obtaining enough
pseudoranges and navigation messages from MVDR
channels.
Channel #12
Channel #12
Channel #12
Channel #2
Channel #1Tracking
Channel #2
Channel #1Tracking
Channel #2
Channel #1Tracking
Element#1
IF data
AdaptiveBeamforming
MVDR (CH1~12)
Weight &
Sum
11
14
141
11
12
121
Channel #12
Channel #2
Channel #1Tracking
Positioning
Channel #12
Channel #2
Channel #1Tracking
11
13
131
Steering Vector
141
131
121
1
j
j
j
e
e
e
Element#2
IF data
Element#3
IF data
Element#4
IF data
AdaptiveBeamforming
Power Minimization
(CH 13)
Weight &
Sum
Channel #12
Channel #2
Channel #1Tracking
Figure 4. Block diagram of the software architecture
Figure 5. Architecture of Space-Time Adaptive Processing
Figure 6. Screenshot of CRPA software receiver GUI
Figure 6 shows the graphical user interface (GUI) of
CRPA software receiver. It includes several useful plots
for showing receiver performance and jammer
information. In this example, there is a jamming source in
the direction of -45º azimuth as seen in the Gain Pattern
Plot (there is a null in blue at this azimuth) or Angle
Frequency Response plot. The Gain Pattern Plot is a
composite of the gain pattern for all MVDR channels.
Hence, it is useful for showing the nulls, which should be
common to all channels, but not the beams, which depend
on the satellite tracked in each channel. There is a deep
null in the gain pattern as well as the angle-frequency
response. The CRPA software receiver is tracking 12
satellites as seen in the C/No Plot. For each satellite (e.g.
PRN 2) there are six columns indicating the C/No for
different processing forms. Columns 1 and 2 are for
MVDR and PM. Columns 3 to 6 are single antenna
processing for antennas 1 to 4, respectively. Note that
some of satellite channels lose lock because the jammer
direction is close to satellite direction. These are the three
processing approaches (MVDR, PM, and single antenna)
that will be used to quantify the benefits of CRPA.
OVERVIEW OF FIELD TESTS
We participated in several live-jamming tests in 2012 and
demonstrated the performance of the CRPA software
receiver. Our general objectives are demonstrations of
anti-jam performance in numerous scenarios, including
comparison of different processing techniques and
analyses of different hardware effects. Tests include two
test campaigns and one self-test listed in table 1.
Table 1. Descriptions of tests Name Date Location
DHS June,
2012 White Sands, NM
Sweden Oct,
2012
Robotförsöksplats
Norrland (RFN), Sweden
Woodside Nov,
2012 Woodside, CA
DHS TEST CAMPAIGN
The Department of Homeland Security sponsored the
Gypsy jamming exercise in White Sands Missile Range
(WSMR) in June, 2012. In this multi-day exercise, there
were many dynamic and static scenarios. Dynamic
jamming scenarios used multiple 250 milliWatt (mW) or
2.5 Watt (W) jammers on vehicles at approximately 40
miles per hour (mph). We sited our CRPA about 5 meters
to the side of one of the main roads for the dynamic test
scenarios. For static scenario, multiple 25 W jammers
were operated from several locations throughout the test
range. The CRPA was located in between several
jammers to test the capability to reject multiple jammers
with different direction.
A. DYNAMIC SCENARIOS
The dynamic scenario equipment set up placed the
Stanford CRPA about 5 meters off a North-South running
road traversed by up to two jamming vehicles. The
location was near the turnaround point of the vehicles
allowing for at least two jamming passes from each
vehicle – a South bound and North bound pass. A
separate Ublox receiver was also sited nearby. Due to the
proximity of the CRPA to the road, the receiver
experienced very strong jamming. This resulted in very
low C/No during the short period of time when the
vehicle passed by the antenna. Since the second jamming
vehicle only trailed the first by a few minutes, there was
little recovery time for re-acquisition between the first and
second jammer. To better quantify the full benefits of the
CRPA, the CRPA processed IF was input to a commercial
high-sensitivity receiver (Ublox) in order to utilize the
better C/No thresholds and fast re-acquisition of that
receiver. In order to have a fair comparison between
CRPA processing and a single antenna, all signals of
interest (MVDR processed, PM processed and single
antenna) were played back through a commercial high-
sensitivity receiver shown in figure 7. The CRPA
processing is the result of weight-and-sum from four
antenna data sets to single data set and forms a CRPA
processed IF signal.
Figure 7. Playback procedure for comparing
performance
Figure 8.
Left : jammer’s path in the DHS dynamic scenario
Right : location of CRPA software receiver
The jammer’s path and is shown in figure 8. Two 2.5W
mobile jammers were separated by about four-minute.
These vehicles passed by the SU CRPA twice each as
they turned around shortly after passing the test location.
The comparison of C/No results and J/N is shown in
figure 9. The blue curve shows the J/N which has four
peaks of up to 32 dB due to the jammers’ proximity to the
CRPA. Three C/No curves are shown for performance
and comparison. They are SU MVDR in red, SU PM in
green and ublox single antenna in black. Figure 10 shows
the C/No histogram of these three cases and their percent
outage. The SU MVDR C/No has the highest C/No value
due to a 6 dB gain from beamsteering and no outage of
tracking. The Ublox single antenna C/No has lowest value
and the most outages (7%).
0 200 400 600 800 1000 1200 1400 1600
5
10
15
20
25
30
35
40
45
50
55
Time (s)
C/N
o (
dB
-Hz)
SU MVDR C/No
SU PowerMin C/No
ublox C/No
J/N
0 200 400 600 800 1000 1200 1400 16000
10
20
30
40
50
60
70
80
90
100
J/N
(d
B)
Figure 9. Comparison of C/No results and J/N in the
DHS dynamic scenario
0 10 20 30 40 50 600
10
20
30
40C/No Histo of ublox
Perc
enta
ge (
%)
7.43%
Outage
0 10 20 30 40 50 600
10
20
30
40C/No Histo of PowerMin
Perc
enta
ge (
%)
0.12%
Outage
0 10 20 30 40 50 600
10
20
30
40C/No Histo of MVDR
Perc
enta
ge (
%)
0.00%
Outage
Figure 10. C/No histogram and outage in the DHS
dynamic scenario
B. STATIC SCENARIOS
The static scenarios had jammers spread over the northern
half of WSMR – an area of about 30 km in radius. From
the SU test location, three jammers of the total six shown
in the figure 11 were detected. The other jammers were
blocked by mountainous terrain or too far from the test
site. The jammers were turned on in sequential order. The
first jammer was on in 50 second into the data collection.
The others were on after around 680 second of data
collecting. Figure 12 shows the composite gain pattern at
the end of scenario. There are three deep nulls in the
directions of three jammers. Figure 13 shows the C/No
results along with the corresponding J/N. When the first
jammer is on, there is no significant decrease in the C/No
of each processing method. This is due to the low level of
received jamming power. However, when other jammers
are turned on with J/N increasing 10 dB, all C/No
noticeably decrease though by different amounts. The
single antenna drops the most - by about 8 dB. MVDR
and PM drop 7 dB and 5 dB, respectively. The difference
between CRPA and single antenna C/No during this
jamming is less than the previous mobile scenario because
the nulls need to be directed in three different directions
resulting in nulls that are not as deep as before. A sense of
the effect is seen in that PM has a smaller C/No drop than
MVDR. PM has more degrees of freedom than MVDR
since it is not constrained by beamsteering. So it can form
slightly better nulls. However, it is important to note that
MVDR still performs better as the beamsteering gain
outweighs the slightly deeper nulls.
Figure 11. Map of jammers and CRPA software
receiver in the DHS static scenario
Figure 12. Gain pattern with three static jammers
0 100 200 300 400 500 600 700 800 9000
5
10
15
20
25
30
35
40
45
50
Time (s)
C/N
o (
dB
)
SU MVDR C/No
SU PowerMin C/No
Single C/No
Jammer J/N
0 100 200 300 400 500 600 700 800 9000
5
10
15
20
25
30
35
40
45
50J/N
(d
B)
Figure 13. Comparison of C/No results and J/N in the
DHS static scenario
SWEDEN TEST CAMPAIGN
The Swedish jamming test in Oct 2012 had more
powerful jammers up to 50 dB J/N and numerous types of
jamming waveforms. There are several static scenarios
using different type of jammers. Figure 14 shows location
of the jammer and the SU CRPA. The distance between
them is about 10 meters. The antenna array used in the
Sweden testing is comprised of four commercial patch
antennas, which were arranged in square or Y layout
shown in figure 15. Some representative scenarios in
which the jammer power ramps from 20 dB to 50 dB J/N
are shown. Three types of jammer are used for test -- 1)
swept CW 2) wideband noise 3) 2 MHz bandwidth. In
these scenarios, the anti-jam capability of our CRPA
software receiver is characterized in term of maximum
tolerable J/N without losing lock.
Figure 14. Location of jammer and receiver in the
Sweden testing
Figure 15. Antenna array used in the Sweden testing
The spectrums of three jammers are shown in the figures
16, 17 and 18. The C/No vs. J/N of three scenarios are
shown in figures 19, 20 and 21. The C/No results of
MVDR, PM and single antenna to a commercial receiver
are compared. An overall summary of performance is
listed in table 2. In conclusion, the CRPA processing can
provide around 20 dB of gain in the anti-jam performance
compared to single antenna receiver.
Table 2. Summary of maximum tolerable J/N
Swept
CW
Broadband
Noise
2 MHz
BW
MVDR > 47 dB 46 dB 50 dB
PowerMin > 47 dB 43 dB 47 dB
ublox 23 dB 23 dB 29 dB
Gain
with CRPA 24 dB 20~23 dB 18~21 dB
-1.5 -1 -0.5 0 0.5 1 1.5 2-120
-100
-80
-60
-40
-20
0
20
40
Frequency (MHz)
Pow
er/
frequency (
dB
/Hz)
Power Spectral Density
Figure 16. Spectrum of swept CW in the Sweden
testing
-1.5 -1 -0.5 0 0.5 1 1.5 2-100
-80
-60
-40
-20
0
20
40
60
Frequency (MHz)
Pow
er/
frequency (
dB
/Hz)
Power Spectral Density
Figure 17. Spectrum of wideband noise in the Sweden
testing
-1.5 -1 -0.5 0 0.5 1 1.5 2-140
-120
-100
-80
-60
-40
-20
0
20
40
Frequency (MHz)
Pow
er/
frequency (
dB
/Hz)
Power Spectral Density
Figure 18. Spectrum of 2MHz bandwidth jammer in
the Sweden testing
0 200 400 600 800 10000
5
10
15
20
25
30
35
40
45
50
55
Time (s)
C/N
o (
dB
-Hz)
SU MVDR C/No
SU PowerMin C/No
ublox C/No
Jammer J/N
0 200 400 600 800 10000
5
10
15
20
25
30
35
40
45
50
55
J/N
(d
B)
Figure 19. C/No vs. J/S of swept CW in the Sweden
testing
0 100 200 300 400 500 600 7000
5
10
15
20
25
30
35
40
45
50
55
Time (s)
C/N
o (
dB
-Hz)
SU MVDR C/No
SU PowerMin C/No
ublox C/No
Jammer J/N
0 100 200 300 400 500 600 7000
5
10
15
20
25
30
35
40
45
50
55
J/N
(d
B)
Figure 20. C/No vs. J/S of wideband noise in the
Sweden testing
0 100 200 300 400 500 6000
5
10
15
20
25
30
35
40
45
50
55
Time (s)
C/N
o (
dB
-Hz)
SU MVDR C/No
SU PowerMin C/No
ublox C/No
Jammer J/N
0 100 200 300 400 500 6000
5
10
15
20
25
30
35
40
45
50
55
J/N
(d
B)
Figure 21. C/No vs. J/S of 2MHz bandwidth jammer in
the Sweden testing
WOODSIDE L5 TEST
The SU CRPA was taken to Woodside VHF Omni
direction Ranging (VOR)/Tactical Air Navigation
(TACAN) (VORTAC) for testing as the DME portion of
Woodside VORTAC (FAA identifier OSI) transmits on
1173 MHz, which is in the center of the GPS L5 band.
Thus the test provided an opportunity to demonstrate the
SU CRPA software receiver capability for operating on
L5. Figure 22 shows a map of Woodside VORTAC with
the location of the DME transponder. The figure also
shows the antenna array which was placed only a few
meters from the DME transponder. The antenna array
utilized four Trimble Zephyr antennas and was arranged
in a Y layout. Figure 23 shows the amplitude of GPS L5
collected signal with time. DME pulse pairs were present
with 4% duty cycle over the duration of the collection.
Because the antenna array was located only 5 meters
away from the 100 W transponder, the DME pulse pairs
saturated the USRP as seen in figure 24. The blue dash
curve is the extrapolated DME pulse pair based on the
received measurements. So the received signal in the red
curve will saturate if the blue curve is beyond the
saturation limit shown in black curve. However, the
receiver still can track the L5 signals from three WAAS
geostationary satellites (GEOs) and one GPS satellite,
PRN 25, as seen in figure 25. Figure 26 shows the C/No
vs. duty cycle of DME signal. The black curve is the
playback result of single antenna data set to NovAtel
OEMV-3 receiver. It takes about 25 seconds to acquire
signal. After that, there is one dropout in the NovAtel
single antenna C/No. The MVDR and PM C/No results
show that CRPA processing allowed the receiver to
remain in lock.
Figure 22. Left : satellite view of Woodside VORTAC
Right : location of antenna array and DME
transponder in Woodside
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000
2000
4000
6000
8000
10000
12000
14000
16000
18000
Time(s)
Am
plitu
de
GPS L5 Collected Signal in Woodside VORTAC
GPS L5
Figure 23. Amplitude of L5 collected signal in the
Woodside testing
0 10 20 30 40 50 60 70 800
2000
4000
6000
8000
10000
12000
14000
16000
Time(s)
Am
plitu
de
GPS L5 Collected Signal in Woodside VORTAC
GPS L5
Regular DME
Extrapolated GPS L5
Saturation Limit
Figure 24. Amplitude of L5 collected signal compared
to regular DME pulse pair
60
-120
30
-150
0
180
-30
150
-60
120
-90 90
25
133135 138
Figure 25. Skyplot of L5 in the Woodside testing
0 50 100 150 200 250 300 3500
5
10
15
20
25
30
35
40
45
50
55
Time (s)
C/N
o (
dB
-Hz)
SU MVDR C/No
SU PowerMin C/No
NovAtel Single C/No
DME duty cycle
0 50 100 150 200 250 300 3502
2.5
3
3.5
4
4.5
5
5.5
6
Pe
rce
nta
ge
(%
)
Figure 26. C/No vs. duty cycle of DME signal in the
Woodside testing
SUMMARY
Stanford has designed and implemented a real-time
CRPA software receiver using inexpensive COTS
elements. This receiver has been validated in three field
tests. The beam forming algorithms implemented in the
receiver can rapidly update the gain pattern of antenna to
null dynamic jammers moving at 200 degrees/second (40
mph at a distance of 5 meters) relative to the antenna. Our
CRPA receiver has the capability to mitigate over 40 dB
J/N jammers for three types 1) swept CW 2) broadband
noise 3) 2MHz bandwidth. In comparison to a
commercial single-antenna receiver, our CRPA software
receiver can provide at least 20 dB gain for the anti-jam
performance in these scenarios. We also successfully
tested the CRPA receiver for processing the L5 signal
under an environment with the pulse-type/high-power
DME signal. This work is potentially the first real-time
CRPA ever tested for L5 in the open literature.
Additionally, the testing allow for the characterization of
A/J performance of a commercial system using the latest
technologies. A playback procedure was created to replay
the signals from recorded and CRPA processed data. This
procedure allowed for the combination of CRPA
processing with the latest high sensitivity, fast
reacquisition commercial receiver.
ACKNOWLEDGMENTS
The authors gratefully acknowledge of John K. Merrill
and Michael Bergman from Department of Homeland
Security (DHS) for organizing DHS jamming exercise.
The authors gratefully acknowledge Fredrik Marsten
Eklöf from Swedish Defense Research Agency for
organizing the Sweden testing. The authors gratefully
acknowledge Dan Specht from Federal Aviation
Administration (FAA) for providing us access to the
Woodside VORTAC facility. The authors gratefully
acknowledge Gabriel Wong’s assistance for replaying L5
signal to NovAtel Receiver. The authors gratefully
acknowledge the FAA CRDA 12-G-003 for supporting
this research.
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